This relates to techniques for electronically specifying the location of objects on a planar surface.
Depth-sensing cameras can be used to identify the location of objects captured by the camera, because the depth data provided by the camera provides information that can be used to infer where different objects are located. Particularly in the case of objects located on a planar surface such as a table, it is valuable to know exactly where those objects are located in a variety of different operations. For example, a computer may be operated from the tabletop by simply making typing movements without any keyboard. The camera can be used to determine which finger is moved and to correlate that movement to a keystroke.
As another application, user gestures made on the tabletop may be correlated to computer commands.
Similarly objects placed on the tabletop may be located on the table using depth-sensing camera and the depth data that it produces. For example, someone playing a game could do so without having an actual board but simply move pieces on the table so they could appear on a computer screen as if they are on a game board.
In short, an ordinary depth-sensing camera can enable interactive functionality on an uninstrumented planar surface, such as a tabletop. In order to make effective use of this interactive functionality, it may be desirable to segment objects, both on and above the tabletop, to support both input sensing and interaction. An enabling step in such segmentation is a one-time calibration to compute the tabletop's planar surface. In such a calibration all the objects are removed from the tabletop and a best fit plane is calculated. This calculation identifies the table's three-dimensional position relative to the depth-sensing camera and its extent. These values enable segmentation, even when the camera is angled, as opposed to orthogonal, to the planar surface or tabletop.